1. Field of the Invention
The present invention relates to an endoscope that includes a bending portion on a distal end side of an insertion section.
2. Description of the Related Art
An endoscope is conventionally widely used in a medical field and other fields. For example, the endoscope is used, through insertion of an elongated insertion section into a subject, in observation of a target site in the subject, and in various kinds of treatment with use of treatment instruments that are inserted into a treatment instrument channel as necessary. The endoscope of this type typically includes a bending portion on a distal end side of the insertion section, and a direction of the distal end portion is changed through operation of an operation section.
Incidentally, in the endoscope having the bending portion, built-in components that are easily influenced by bending operation are desirably disposed at respective positions close to the center in a bending tube as much as possible in order to secure durability, workability, and the like of the built-in components in the bending tube. At the same time, favorable displacement of the respective built-in components in the bending tube is not necessarily coincident with favorable displacement of the respective corresponding functional portions at the distal end portion. Thus, in the endoscope of this type, measures such as appropriate change of the displacement of the built-in components in the bending tube, inside the bending portion are performed. For example, Japanese Patent Application Laid-Open Publication No. 2006-288759 discloses a technology in which a light guide that has rigidity lower than rigidity of the other built-in components and has a concern about buckling or the like due to the bending operation is disposed at a position close to the center in the bending tube, in the middle in the insertion axis direction of the bending portion, and is disposed at a position close to an outer circumference in the bending tube in association with the displacement of an illuminating window of the distal end portion, on a distal end side in the insertion axis direction of the bending portion (see FIGS. 11 and 12 in Japanese Patent Application Laid-Open Publication No. 2006-288759 mentioned above).